1. Field of Invention
The present invention pertains to the field of micro-movers for information storage. More particularly, this invention relates to providing micro-movers for parallel plate information storage devices wherein the movement of an array of micro-movers is coordinated to balance dynamics.
2. Background
Memory devices using parallel plates with read-write transducers on one plate and a recording medium on the other plate usually require micro-movers to drive planar motion of the plates relative to each other. The combined motion of plates in the X and Y directions enhance data transfer rates to and from the recording medium. Micro electro mechanic system (MEMS) motors are used to move plates relative to each other. Such a MEMS motor is shown in U.S. Pat. No. 5,986,381 granted to Hoen et al. on Nov. 16, 1999 in which an array of drive electrodes is mounted on a surface of one member and an array of matching driven electrodes is disposed on an opposing surface of a second member. Voltage patterns on the drive electrodes and driven electrodes cause the members to move relative to each other. The spacing, number, pitch and voltages on the electrodes control movement of one member relative to the other.
In order to achieve the high information density and speed required of current information storage systems, great accuracy and speed are required in the movements of the plates with tight control over the ranges of motion in the all three X, Y and Z orthogonal directions. An example of such a high-speed precisely controlled micro-mover motor used with an information storage system is described in U.S. Pat. No. 5,834,864 granted to Hesterman et al. on Nov. 10, 1998. This system provides for at least one pair of silicon plates, one having read-write elements and the other providing a plurality of information storage areas. One or both the plates includes a structure of etched silicon springs controlling the range and resilience of movement of the plate in the X direction or the Y direction. Another embodiment uses silicon springs on a single plate to control movement in both X and Y directions.
Micro-movers are generally micro-machined in multiples on a single chip, oriented in an orthogonal pattern. Typically, groups of micro-movers on a chip utilize a single drive control and may move simultaneously. Plates, such as those shown in Hesterman et al. may do random seeks or may oscillate in a direction at or near resonance, such as 1000 Hz. Typical plates may have up to 10,000 transducers in a 100xc3x97100 array. Data is transferred in parallel bytes, with as many as 300-400 plates moving simultaneously at accelerations up to 50 Gs. Since each plate may have a moving mass of about 35 milligrams, considerable vibration can be generated by MEMS driven storage units in operation. These mechanical stresses may lead to premature wear on the MEMS motors and possible inaccuracies in data transfer.
The problem of imbalance and vibration is increased in applications that typically operate in a vacuum to minimize interference from stray particles. The absence of atmospheric damping increases the likelihood of vibration from multiple simultaneous operating micro-movers. The delicacy of operations and structure at atomic resolution levels can be dramatically affected by vibration amounts that would not be a problem at a less miniature scale. Accordingly, coordinating and controlling the simultaneous movement of the information storage components are needed to provide dynamic balance for MEMS micro-movers.
The present invention provides for a plurality of micro-movers coordinated to move in opposing directions to provide dynamic balance to a MEMS driven information storage system. Preferably an even number of micro-motors move opposite to each other to cancel inertial imbalance in the system. Alternately, in the event that different plates have different moving masses, the movement of the micro-motors is coordinated to provide equal momentum in opposing directions of the moving masses.
Since plates and micro-motors typically move in both X and Y directions, opposing motions of plates must be coordinated in X and Y directions. Simultaneous information transfer occurs in bytes utilizing two quadrants that can make use of four plates each. Thus, a preferred embodiment of the present invention utilizes sets of four plates driven by their respective micro-movers to move together in opposing directions. To avoid undesirable torque, one plate of a first coordinated plate pair is disposed on a first common axis with a plate of a second coordinated plate pair. The other plate of the first plate pair is disposed on a second common axis with a plate of a third coordinated plate pair. Other plates in the array are similarly disposed to minimize the vibration of the system caused by the momentum of moving plates. In order to accommodate the opposing motions of plates, logic circuitry modifies data flow in order to accommodate opposing motions and make data appear to be contiguous.
A micro-mover system according to the present invention preferably includes a first information storage unit having a first pair of parallel plates closely spaced from each other and disposed relative to each other to enable the exchange of information. A first micro electromechanical system (MEMS) motor is associated with the first information storage unit to move at least one of the first pair of parallel plates in a first plane parallel to the other plate of the first pair to facilitate the exchange of information between the first pair of plates.
A second information storage unit has a second pair of parallel plates closely spaced from each other and disposed relative to each other to enable the exchange of information. The second pair of parallel plates is oriented with respect to the first pair of parallel plates to develop counter movement in opposing directions. A second MEMS motor is associated with the second information storage unit to move at least one of the parallel plates along one of the opposing directions and in a second plane parallel to the other plate of the second pair to facilitate the exchange of information between the second pair of plates.
Control circuitry is associated with the first and second MEMS motors to coordinate the movement of the first and second pairs of plates, so that the motion of the one of the second set of parallel plates along one of the opposing directions occurs at the same time and in a direction opposite to the movement of the one of the first set of parallel plates to thereby cancel a substantial level of total momentum arising from movement within the micro-mover system.
In another preferred embodiment of the present invention, a first group of selected plate pairs includes a first plate moving in a first direction aligned along a common axis with a second plate in a second group of selected plate pairs. The second plate moves in an opposing direction to the first plate, so that opposing movements of the first and second plates are aligned on a common axis to prevent torque forces.
Another preferred embodiment of the present invention comprises a method of storing information in a memory storage system having a plurality of pairs of plates. Each pair of plates is associated with a micro-mover for moving at least one plate relative to the other plate in each pair of plates. A first plate in a first pair of plates is moved in a first direction with a first momentum. A second plate in a second pair of plates is moved in a direction opposite to the first direction with a second momentum approximately equal to the first momentum. The movement of the first and second plates are configured to approximately cancel the first and second momenta.
Another preferred method of storing information in accordance with the present invention includes disposing a plurality of plates in a rectangular array of at least four pairs of plates. A top plate of a first pair of plates is aligned on a first common axis with a second plate of a second pair of plates. A bottom plate of the first pair of plates is aligned on a second common axis with a third plate of a third pair of plates. Such plate alignments on common axes provide offsetting momenta while avoiding creating undesirable torque forces, thereby minimizing vibration in the storage system.
Other aspects and advantages of the present invention will become apparent from the following detailed description, which in conjunction with the accompanying drawings illustrates by way of example the principles of the present invention.